Rechargeable battery with protective circuit

ABSTRACT

A rechargeable battery is integrated with a battery protection circuit that protects the rechargeable battery from overcharging, overdischarging, and so forth. A circuit board ( 9 ) on which are formed a battery protection circuit, a positive input and output terminal ( 4 ), and a temperature detection terminal ( 6 ) is disposed on a rechargeable battery ( 10 ) via a spacer ( 13 ), and the positive and negative electrodes of the rechargeable battery ( 10 ) are connected to the circuit board ( 9 ). This assembly is enveloped by a cover cap ( 15 ) and a cover plate ( 14 ), such that the positive input and output terminal ( 4 ) and the temperature detection terminal ( 6 ) are exposed to the outside through openings provided in the cover plate ( 14 ), and one end of the cover cap ( 15 ) in the same plane as these is used for connection as a negative input and output terminal ( 5 ).

TECHNICAL FIELD

The present invention relates to a rechargeable battery, such as alithium ion rechargeable battery, particularly of a flat shape, which isintegrated with a battery protection circuit so that the rechargeablebattery itself has a function of protecting against overcharging,overdischarging, and so forth.

BACKGROUND ART

Rechargeable batteries are provided with a variety of protectivefunctions for preventing damage to the battery caused by abnormal usesuch as overcharging, overdischarging, short-circuiting between thepositive and negative electrodes, or short-circuiting of the batteryperipheral circuitry of the device in which the battery is used.Examples of these functions include PTC (Positive TemperatureCoefficient) elements that prevent excessive discharge current due toshort-circuiting or the like, and safety vents that release internalpressure by cutting off the power circuit in the event of an abnormalrise in internal pressure caused by overcharging. These protectivefunctions are known as functions incorporated into the rechargeablebattery itself. A lithium ion rechargeable battery is normally providedwith a battery protection circuit to prevent overcharging,overdischarging, and so forth. Such battery protection circuit isgenerally unitized with the battery as part of battery packconfiguration, in which a circuit board that makes up the batteryprotection circuit is integrally contained in the pack case along withthe lithium ion rechargeable battery. It is common knowledge thatbattery packs such as this, in which the rechargeable battery and theprotection circuit are integrally housed in a case, are often used forbattery-powered devices such as cellular telephones and laptopcomputers.

In addition to preventing overcharging and overdischarging as mentionedabove, this battery protection circuit can also have such functions ascutting off excessive current or monitoring cell temperature, and ifthis circuit could be integrated with the rechargeable battery itself,it would be possible to create a rechargeable battery equipped with abattery protection circuit without constituting a battery pack, whichwould make the rechargeable battery more universally applicable.

When a battery protection circuit is integrated with a rechargeablebattery, however, it is difficult to avoid making the externaldimensions larger or losing the original configuration of therechargeable battery. In particular, a flat-shaped rechargeable batteryis made thin so that it can be used in small devices such as portabledevices, and when a battery protection circuit is integrated with such arechargeable battery it is difficult to find space for the circuit boardthat makes up the battery protection circuit, which means that it isdifficult to integrate a battery protection circuit without increasingthe external dimensions.

Also, with a small, flat-shaped rechargeable battery, there is littlespace in which to provide the above-mentioned PTC element or currentcut-off vent, so the elements for electromotive force must be reduced insize in order to ensure this space, the problem with which is that thebattery capacity is diminished. Therefore a PTC element must be providedas part of the battery protection circuit outside the rechargeablebattery, and the battery protection circuit must take over the functionof the current cut-off vent. However, if a PTC element is provided aspart of the battery protection circuit, then an increase in volume isinevitable when the battery protection circuit is integrated with therechargeable battery, which is contrary to the objective of minimizingthe increase in external dimensions. Also, reliability suffers when anordinary battery protection circuit is made to take on the function of acurrent cut-off vent, making it difficult to obtain a level ofreliability at which the rechargeable battery will definitely beprotected.

It is an object of the present invention to provide a battery equippedwith a battery protection circuit, with which a compact constructionthat can be applied to a flat-shaped rechargeable battery minimizes theincrease in the external dimensions of the rechargeable battery, andwith which the battery can be protected by enhancing the function of thebattery protection circuit and without providing a PTC element or acurrent cut-off vent, and which can be used by itself as a battery,without a battery pack configuration being required.

DISCLOSURE OF THE INVENTION

To achieve the above object, a first aspect of the present inventionprovides a rechargeable battery equipped with a battery protectioncircuit for protecting this rechargeable battery from overcharging andoverdischarging, comprising:

a cell case made of a bottomed cylindrical container, containing thereinelements for electromotive force;

a sealing plate for sealing an open end of said cell case;

a protruding terminal provided insulated from the cell case on saidsealing plate, said cell case and said protruding terminal beingrespectively assigned as a positive electrode and a negative electrodeof the rechargeable battery;

a connection piece joined to the protruding terminal, a circuit boardwhich includes a plurality of input and output terminals and constitutesa battery protection circuit, and to which said connection piece isconnected at a specific location, and a spacer that keeps the circuitboard and the cell case apart, all of which are disposed at one end onthe side of the sealing plate of the cell case; and

a cover cap disposed so as to envelop the circuit board, the spacer, andthe connection piece in a state in which said plurality of input andoutput terminals on the circuit board are exposed to the outside, and atthe same time to cover the peripheral part of the cell case, said covercap being connected at a specific location of the circuit board.

With the above structure, the rechargeable battery and the circuit boardare electrically connected by the cover cap and the connection piecethrough the positive and negative electrodes of the rechargeablebattery, and are integrated by the cover cap. Because the input andoutput terminals provided on the circuit board are exposed on theoutside, the rechargeable battery with its internally integrated batteryprotection circuit can be handled and used just the same as arechargeable battery alone.

In the above structure, the cover cap can be provided so as to cover theentire surface of the peripheral part of the cell case, which securelymaintains the integration of the rechargeable battery and the circuitboard that makes up the battery protection circuit.

Also, if at least one inward cutout is formed in the peripheral part ofthe cover cap, this is bent inward to hit the top of the cell case, andat least one opening is formed in the peripheral part after it has beenbent, the cover cap will be fixed more securely to the rechargeablebattery, and at the same time an opening will be formed communicatingwith the sealing assembly of the rechargeable battery, thereby forming agas escape hole for releasing any abnormally high pressure inside therechargeable battery.

The plurality of input and output terminals provided on the circuitboard can be disposed asymmetrically, which prevents the cell from beinginstalled backwards.

The outside of the circuit board can be covered with a cover plateprovided with windows that open over the input and output terminals,which protects the circuit board.

If the outer side of the mounting location of an IC disposed on theinner side of the circuit board is at least 0.1 mm away from the coverplate, then the electrical effect caused by the application of pressurefrom the outside to the IC can be prevented.

If the connection piece is disposed on the protruding terminal of therechargeable battery, and the underside of the circuit board issupported by this connection piece alone or by both the connection pieceand the spacer, then the input and output terminals, which are subjectedto contact pressure from the device side, will be supported from theirunderside, so stable connected is achieved.

If positioning components with respect to the rechargeable battery areformed in the spacer, it will be easier to install the spacer on therechargeable battery.

If a notch is formed in the spacer at a location corresponding to thecutout formed in the cover cap, this will ensure a gas escape passagecommunicating with the opening formed by the cutout from therechargeable battery.

If a conductor pattern connected to a ground potential is formed on atleast the outer side of the circuit board at the location where thebattery protection circuit (IC) is disposed, then a shielding effectwill also be obtained from the conductor pattern, and the electricaleffect that electromagnetic waves emitted from the device side wouldotherwise have on the IC can be prevented.

If the conductor pattern formed directly under the battery protectioncircuit is connected at a proximal location to a thermistor disposed onthe inner side of the circuit board, then the temperature of the IC,which conducts heat through the conductor pattern, can be sensed by thethermistor, and the thermistor that is on the inner side of the circuitboard and detects the generation of heat in the rechargeable batterywill also be sensitive to the heat of the IC and can be used fortemperature sensing of the rechargeable battery and the IC.

If the connection piece is such that the portion joined with theprotruding terminal is formed in a thickness corresponding tothe.distance between the protruding terminal and the circuit board, andconnecting leads to the circuit board are formed at both ends, then themiddle part of the circuit board can be supported by the connectionpiece.

If the side peripheral surface is covered with an electricallyinsulating sheet, then the side peripheral surface where one of thepolar terminals of the cell is exposed will be insulated and covered,allowing unexpected short-circuiting to be prevented.

If a perforated line surrounding the opening formed in the cover cap isformed in the sheet at a location corresponding to this opening, thenthe opening used for gas escape will not be blocked off, and instead thesheet will tear out along the perforated line during gas release.

If at least one, and preferably all, of the connection piece, the inputand output terminals, and the cover cap is or are formed from anickel-copper alloy, then there will be better compatibility to joiningby soldering, spot welding, and so forth, affording better compatibilityto the type of joining means used at the connection location.

A second aspect of the present invention provides a rechargeable batteryequipped with a battery protection circuit for protecting thisrechargeable battery from overcharging and overdischarging, comprising:

a cell case made of a bottomed cylindrical container, containing thereinelements for electromotive force;

a sealing assembly for sealing an open end of said cell case;

a protruding terminal provided insulated from the cell case on saidsealing assembly, said cell case and said protruding terminal beingrespectively assigned as a positive electrode and a negative electrodeof the rechargeable battery;

a connection piece joined to said protruding terminal, a circuit boardon which a battery protection circuit is formed and on which a pluralityof input and output terminals are formed, and a spacer that forms a seatfor the circuit board and keeps the circuit board and the rechargeablebattery apart, all of which are disposed at one end on the side of thesealing assembly of the cell case;

a lead plate joined to the cell case, said lead plate and saidconnection piece being respectively connected at specific locations ofthe circuit board so that the rechargeable battery and the circuit boardare integrated, and the rechargeable battery and the battery protectioncircuit are electrically connected, with the positive and negativeelectrodes of the rechargeable battery being connected via the batteryprotection circuit to said respective input and output terminals of thecircuit board;

an upper insulation board disposed on the circuit board with openingsformed at locations corresponding to said input and output terminals;

a lower insulation board disposed on a bottom surface of the cell case;and

an insulating sheet for covering the entire side peripheral surface ofthe cell case between peripheral edges of the upper insulation board andthe lower insulation board.

With the above structure, because the circuit board is disposed on therechargeable battery via a spacer, and the rechargeable battery isconnected to the battery protection circuit on this circuit board by theconnection piece and the lead plate, the rechargeable battery is formedas a rechargeable battery equipped with a battery protection circuitconnected to the input and output terminals formed on the circuit boardthrough the battery protection circuit. By insulating and covering allof this rechargeable battery except for the input and output terminalswith the upper insulation board, the lower insulation board, and theinsulating sheet, the resulting rechargeable battery equipped with abattery protection circuit has a compact configuration in which just theinput and output terminals are exposed on the outside.

A third aspect of the present invention provides a rechargeable batteryequipped with a battery protection circuit for protecting thisrechargeable battery from overcharging and overdischarging, comprising:

a cell case made of a bottomed cylindrical container, containing thereinelements for electromotive force;

a sealing assembly for sealing an open end of said cell case;

a protruding terminal provided insulated from the cell case on saidsealing assembly, said cell case and said protruding terminal beingrespectively assigned as a positive electrode and a negative electrodeof the rechargeable battery;

a connection piece joined to said protruding terminal, a circuit boardon which a battery protection circuit is formed and on which a pluralityof input and output terminals are formed, and a spacer that forms a seatfor the circuit board and keeps the circuit board and the rechargeablebattery apart, all of which are disposed at one end on the side of thesealing assembly of the cell case;

a lead plate joined to the cell case, said lead plate and saidconnection piece being respectively connected at specific locations ofthe circuit board so that the rechargeable battery and the circuit boardare integrated, and the rechargeable battery and the battery protectioncircuit are electrically connected, with the positive and negativeelectrodes of the rechargeable battery being connected via the batteryprotection circuit to said respective input and output terminals of thecircuit board, thereby constituting a rechargeable battery with abattery protection circuit; and

a pack case in which openings are formed at locations corresponding tosaid input and output terminals for accommodating therein saidrechargeable battery with the battery protection circuit.

With the above structure, because the circuit board is disposed on therechargeable battery via a spacer, and the rechargeable battery isconnected to the battery protection circuit on this circuit board by theconnection piece and the lead plate, the rechargeable battery is formedas a rechargeable battery equipped with a battery protection circuitconnected to the input and output terminals formed on the circuit boardthrough the battery protection circuit. By housing this rechargeablebattery in a pack case having openings at locations corresponding to theinput and output terminals, the resulting rechargeable battery equippedwith a battery protection circuit has a compact configuration in whichjust the input and output terminals are exposed on the outside.

In the above structure, if the connection piece and the lead plate areconnected to the circuit board by a pair of leads, then the circuitboard will be supported more securely on the rechargeable battery.

The plurality of input and output terminals provided on the circuitboard can be disposed asymmetrically, which prevents the cell from beinginstalled backwards.

The conductor patterns formed on the circuit board can be used directlyas the input and output terminals, allowing the cell to be used in afixed state in which it is not removed the device in which it is used.

The input and output terminals can comprise metal sheets joined toconductor patterns formed on the circuit board, which allows the cell tobe used in applications in which it can be removed from the device.

If positioning components for the rechargeable battery and a housingcomponent for the electronic parts mounted on the circuit board areformed in the spacer, then the spacer can be positioned on therechargeable battery, the thickness of the electronic parts on thecircuit board located thereon will be absorbed within the spacer, andthe space taken up by the circuit board can be kept to a minimum.

If the spacer is adhesively joined to the rechargeable battery, thecircuit board can be positioned and held at the proper location.

The insulating sheet can be formed from a material that isheat-shrinkable and self-adhesive, which allows the constituent elementsto be securely enveloped, and a rechargeable battery with an attractiveappearance to be formed.

The insulating sheet can have a design on its surface, which provides anattractive appearance and at the same time allows usage instructions,warnings, or the like to be indicated.

If steps for determining the covering position of the insulating sheetare formed around the peripheral edges of the upper insulation board andthe lower insulation board, the tail end of the covered insulating sheetcan be accommodated within these steps.

A recess for accommodating the lead plate and a recess into which thebottom of the cell case fits can be formed in the lower insulationboard, which allows the lead plate to be accommodated and positioned atthe bottom surface of the rechargeable battery.

If the battery protection circuit is equipped with a main controlcircuit and a sub-control circuit for redundantly protecting therechargeable battery from overcharging, then the rechargeable batterywill be redundantly protected from overcharging that could damage it,eliminating the need for other means for preventing excessive current.

The battery protection circuit can be configured as a circuit with noPTC by being a circuit for preventing excessive current, whichallows-the battery protection circuit to be more compact.

The configuration of the battery protection circuit allows therechargeable battery to have no PTC in its interior, and eliminating thePTC makes it possible to increase the volume of the elements forelectromotive force and raises the cell capacity.

Since overcharging is effectively prevented by the redundantanti-overcharging function had by the battery protection circuit,increases in the internal cell pressure due to overcharging areprevented, so the rechargeable battery does not have to have a currentcut-off vent in its interior, which makes it possible to increase thevolume of the elements for electromotive force and raises the cellcapacity.

A fourth aspect of the present invention provides a rechargeable batteryequipped with a battery protection circuit for protecting thisrechargeable battery from overcharging and overdischarging, comprising:

a cell case made of a bottomed cylindrical container, containing thereinelements for electromotive force;

a sealing assembly for sealing an open end of said cell case;

a protruding terminal provided insulated from the cell case in themiddle of said sealing assembly, said cell case and said protrudingterminal being respectively assigned as a positive electrode and anegative electrode of the rechargeable battery;

a circuit board disposed on the sealing assembly, on which are formed abattery protection circuit and a plurality of input and outputterminals, the protruding terminal and the cell case being connected tosaid input and output terminals via said battery protection circuit;

an upper insulating holder which is disposed at one end on the side ofthe sealing assembly of the cell case and in which openings are formedat locations corresponding to the input and output terminals;

a lower insulating holder disposed at the bottom of the rechargeablebattery, said upper insulating holder and said lower insulating holderrespectively covering an upper and a lower parts of the rechargeablebattery; and

an insulating sheet for covering the peripheral side surface of therechargeable battery.

With the above structure, the positive and negative electrodes of therechargeable battery are connected to a plurality of input and outputterminals formed on the circuit board via a battery protection circuit,and the surrounding area thereof is insulated and covered by aninsulating sheet and an upper insulation holder and a lower insulationholder provided with openings at locations corresponding to the inputand output terminals. A rechargeable battery equipped with a batteryprotection circuit can be achieved merely by providing enough space forthe circuit board to be disposed on the sealing assembly of therechargeable battery, without losing the original configuration of therechargeable battery.

A fifth aspect of the present invention provides a rechargeable batteryequipped with a battery protection circuit for protecting thisrechargeable battery from overcharging and overdischarging, comprising:

a cell case made of a bottomed cylindrical container, containing thereinelements for electromotive force;

a sealing assembly for sealing an open end of said cell case;

a protruding terminal provided insulated from the cell case in themiddle of said sealing assembly, said cell case and said protrudingterminal being respectively assigned as a positive electrode and anegative electrode of the rechargeable battery;

a connection piece joined to the protruding terminal, a circuit board onwhich a battery protection circuit and a plurality of input and outputterminals are formed, and a spacer that forms a seat for the circuitboard and keeps the circuit board and the rechargeable battery apart,all of which are disposed at one end on the side of the sealing assemblyof the cell case;

a lead plate connected to the cell case, said lead plate and saidconnection piece being each connected at specific locations of thecircuit board so that the rechargeable battery and the circuit board areintegrated, and the rechargeable battery and the battery protectioncircuit are electrically connected, with the positive and negativeelectrodes of the rechargeable battery being connected via the batteryprotection circuit to the input and output terminals;

an upper insulating holder disposed at one end on the side of thesealing assembly of the cell case, covering the top of the circuitboard, and having openings formed at locations corresponding to theinput and output terminals;

linking members formed at the distal ends of a pair of extensions thatextend from both sides of said upper insulating holder toward the bottomside of the cell case;

a lower insulating holder disposed at the bottom end of the cell case,covering the bottom of the cell case;

linking members formed at the distal ends of a pair of extensions thatextend from both sides of said lower insulating holder toward the sideof the sealing assembly of the cell case, the upper insulating holderand the lower insulating holder being-linked together via said linkingmembers; and

an insulating sheet for covering the side peripheral surface of therechargeable battery including the side peripheral parts of the upperinsulating holder and the lower insulating holder.

With the above structure, the circuit board is arranged on therechargeable battery with the spacer interposed therebetween, and therechargeable battery is connected to the battery protection circuitformed on the circuit board through the connection piece and the leadplate, whereby provided is the rechargeable battery equipped with thebattery protection circuit, connected to the input and output terminalsformed on the circuit board. By covering the rechargeable battery by theupper insulation holder, the lower and insulation holder and theinsulation sheet with only the input and output terminals exposed tooutside, it is possible to obtain a rechargeable battery equipped with abattery protection circuit with only the input and output terminalsexposed to outside.

In the above structure, it is favorable for the rechargeable battery tobe one with a flat shape having an oval cross section, which can be usedas a power source for portable devices that are intended to be small andthin.

The electronic parts mounted at the sealed end of the circuit board canbe disposed at locations corresponding to recesses formed in the sealingassembly of the rechargeable battery, which reduces the amount that thebattery protection circuit protrudes from the rechargeable battery.

If positioning components with respect to the rechargeable battery andthe circuit board, and openings at locations corresponding to theelectronic parts mounted on the circuit board are formed in the spacer,then the spacer will be positioned when mounted on the rechargeablebattery, the electronic parts mounted on the sealing assembly side ofthe circuit board will fit in the openings, and the battery protectioncircuit will take up less space.

If the positioning components are disposed in parallel in the lengthwisedirection of the protruding terminal, then insulation between the cellcase and the connection piece can be increased at the same thatpositioning is performed.

The plurality of input and output terminals provided on the circuitboard can be disposed asymmetrically, which prevents the rechargeablebattery from being installed backwards.

A step for determining the covering position of the insulating sheet canbe formed around the side periphery of the upper insulating holder,which allows the insulating sheet to be positioned while being stuck on.

If covering components that cover the short side surface and part of thelong side surface of the rechargeable battery formed in a flattenedshape are formed for the upper insulating holder and the lowerinsulating holder, then the rechargeable battery and the batteryprotection circuit can be securely integrated, and since the upper andlower insulation holders do not cover the entire rechargeable battery,no change in the exterior dimensions occurs even if repeated chargingand discharging or the like should cause the cell case to swell.

If the upper insulating holder and the lower insulating holder arelinked by the superposition and/or engagement of the linking componentsthereof, the linking will be more secure.

The lead plates can be joined at one end to the bottom surface of thecell case and extend to the sealing assembly side along the short sidesurface of the flattened cell case, which does not increase thethickness of the flat-shape rechargeable battery.

If recesses or openings for accommodating the lead plates are formed inthe extensions of the upper insulating holder and the lower insulatingholder, then the position of the lead plates can be maintained while theincrease in width is minimized.

The battery protection circuit can be a redundant protection circuitcomprising a main control circuit for cutting off thecharging/discharging circuit when a state such as overcharging oroverdischarging is detected, and a sub-control circuit for cutting offthe charging/discharging circuit when there is malfunction in this maincontrol circuit, and the ground locations of the main and sub-controlcircuits can be separated, which results in the pair of lead plates,which are connected at one end to the cell case, being connected to theground locations of the main control circuit and the sub-controlcircuit, between which there is no direct connection, so a closedcircuit is not formed in the ground circuit, and the effect of noisethat would otherwise be caused by a closed circuit can be reduced.

A sixth aspect of the present invention provides a rechargeable batteryequipped with a battery protection circuit for protecting thisrechargeable battery from overcharging and overdischarging, comprising:

a cell case made of a bottomed cylindrical container, containing thereinelements for electromotive force;

a sealing assembly for sealing an open end of said cell case;

a protruding terminal provided insulated from the cell case on saidsealing assembly, said cell case and said protruding terminal beingrespectively assigned as a positive electrode and a negative electrodeof the rechargeable battery;

a circuit board disposed on said sealing assembly, including a batteryprotection circuit and a plurality of input and output terminals,wherein said cell case and said protruding terminal are each connectedto said input and output terminals via the battery protection circuit,thereby constituting an intermediate unit in which the rechargeablebattery and the circuit board are integrated; and

an outer case in which openings are formed at locations corresponding tothe input and output terminals for sealing therein said intermediateunit.

A seventh aspect of the present invention provides a rechargeablebattery equipped with a battery protection circuit for protecting thisrechargeable battery from overcharging and overdischarging, comprising:

a cell case made of a bottomed cylindrical container, containing thereinelements for electromotive force;

a sealing assembly for sealing an open end of said cell case;

a protruding terminal provided insulated from the cell case on saidsealing assembly, said cell case and said protruding terminal beingrespectively assigned as a positive electrode and a negative electrodeof the rechargeable battery;

a connection piece joined to the protruding terminal, a circuit board onwhich a battery protection circuit and a plurality of input and outputterminals are formed, and a spacer that forms a seat for the circuitboard and keeps the circuit board apart from the rechargeable battery,all of which are disposed at one end on the side of the sealing assemblyof the cell case,

a lead plate joined to the cell case, said lead plate and saidconnection piece being each connected at specific locations of thecircuit board so that the rechargeable battery and the circuit board areintegrated, thereby constituting an intermediate unit in which therechargeable battery and the battery protection circuit are electricallyconnected, with the positive and negative electrodes of the rechargeablebattery being connected via the battery protection circuit to the inputand output terminals of the circuit board; and

an outer case in which said intermediate unit is inserted, said outercase being molded by resin molding in the form of a bottomed cylinderhaving an open end, with openings formed in the bottom surface atlocations corresponding to the input and output terminals of the circuitboard, said open end of the outer case being closed to seal theintermediate unit within the outer case.

With the above structures, the circuit board having the batteryprotection circuit is disposed on a sealing assembly of the rechargeablebattery via a spacer, so the battery protection circuit can be connectedto the rechargeable battery with only a minimum of increase inrechargeable battery height, and sealing this rechargeable battery in anouter case provided with openings at locations corresponding to theinput and output terminals allows a rechargeable battery with a compact,integrated battery protection circuit to be produced.

In the above structures, the outer case can be such that the crosssectional outer shape is formed substantially oval with respect to therechargeable battery that is formed in a cross sectional oval shape, andthe inner shape is formed substantially oval corresponding to the outershape of the rechargeable battery, the result of which is that therechargeable battery equipped with a battery protection circuit has arectangular shape that facilitates installation in a device, and at thesame time the strength of the outer case is improved.

The outer case can also be such that sealing pieces that are extensionsof the long side peripheral parts are formed at the open end of abottomed box, these sealing pieces are bent inward and the opposingparts are fused together by hot pressing, thereby closing the open endand sealing the intermediate unit within the outer case, the result ofwhich is that the intermediate unit can be sealed by a one-piece outercase.

It is favorable for the sealing pieces^([2]) to be such that theopposing long sides at the rectangular open end are formed in a notchedshape so that the notches will fit together when the sealing pieces arebent, the result of which is that the fused mass is increased andsealing strength thereby improved.

The sealing pieces can be formed thicker at the fused portions thereof,which provides enough resin to be melted and makes more secure fusionpossible.

If the sealing pieces are sized such that a gap is left between theopposing parts when the sealing pieces are bent, then there will be nooverlap of the opposing pieces due to bending error, and the moltenresin will work its way through the gap into the interior, filling inany gap resulting from dimensional error in the intermediate unit andabsorbing the error.

If bumps are provided to the inner surface of the sealing pieces, thenany gap resulting from dimensional error in the intermediate unit willbe filled in by the bumps, allowing looseness to be prevented.

The outer case can be such that sealing pieces that are extensions ofthe side peripheral parts are formed at the open end of a bottomed box,and after the intermediate unit has been inserted, these sealing piecesare melted inward by hot pressing, thereby closing the open end, inwhich case the open end side of the intermediate unit, where theextended sealing pieces have been melted and inserted on the inside,will be filled in and this open end closed. Even if there is an error inthe height of the intermediate unit, the outer case can be brought tothe specified height by changing the amount of molten resin that flowsinto the gap in the outer case.

The plurality of input and output terminals can be disposedasymmetrically, which prevents the rechargeable battery from beinginstalled in a device backwards.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a plan view of a flat-shaped rechargeable battery applied inthe various embodiments, and FIG. 1B is a cross section of thisflat-shaped rechargeable battery;

FIG. 2 is an oblique view of the rechargeable battery A equipped with abattery protection circuit according to a first embodiment;

FIG. 3 is an oblique view of the assembly structure of rechargeablebattery A in which the various constituent elements thereof areexploded;

FIG. 4 is a cross section of the structure of the battery protectioncircuit provided to the rechargeable battery;

FIG. 5A is a plan view of the structure on the underside of the circuitboard, and FIG. 5B is a plan view of the structure on the top side ofthe circuit board;

FIG. 6A is an oblique view of a variation example of the spacer, andFIG. 6B is a cross section along the VIB—VIB line in FIG. 6A;

FIG. 7 is a circuit diagram illustrating the electrical structure of therechargeable battery equipped with a battery protection circuitaccording to the same embodiment;

FIG. 8A and FIG. 8B are oblique views of variation examples of theconnection piece;

FIG. 9A is a side view of the structure of the rechargeable battery Bequipped with a battery protection circuit according to a secondembodiment, with half of the insulating label covering peeled away, FIG.9B is a plan view of the terminal layout on the top of this cell, andFIG. 9C is a plan view of the structure of the bottom surface;

FIG. 10 is a side view of the assembly structure of rechargeable batteryB in which the various constituent elements thereof are exploded;

FIG. 11 is an oblique view of the structure of the connection piece;

FIG. 12 is an oblique view of the structure of the lead plate;

FIG. 13A is a plan view of the structure on the top side of the spacer,FIG. 13B is a cross section along the XIIIB—XIIIB line in FIG. 13A, andFIG. 13C is a plan view of the structure on the underside of the spacer;

FIG. 14A is a plan view of the front of the circuit board, and FIG. 14Bis a plan view of the back of the circuit board;

FIG. 15 is a circuit diagram illustrating the electrical structure of arechargeable battery equipped with a battery protection circuit;

FIG. 16 is an oblique view of an example in which a cell with a batteryprotection circuit is produced in the form of a battery pack;

FIG. 17A is a plan view of the structure on the top side of the upperinsulation board, FIG. 17B is a cross section along the XVIIB—XVIIB linein FIG. 17A, and FIG. 17C is a plan view of the structure on theunderside of the upper insulation board;

FIG. 18A is a plan view of the structure on the top side of the lowerinsulation board, FIG. 18B is a cross section along the XVIIIB—XVIIIBline in FIG. 18A, and FIG. 18C is a plan view of the structure on theunderside of the lower insulation board;

FIG. 19 is an oblique view of the rechargeable battery C equipped with abattery protection circuit according to a third embodiment;

FIG. 20 is an oblique view of the assembly structure of rechargeablebattery C in which the various constituent elements thereof areexploded;

FIG. 21A is a plan view of the structure on the top side of the spacer,FIG. 21B is a plan view of the structure on the underside of the spacer,and FIG. 21C is a cross section along the XXIC—XXIC line in FIG. 21A;

FIG. 22A is a plan view of the front of the circuit board, and FIG. 22Bis a plan view of the back of the circuit board;

FIG. 23 is a circuit diagram illustrating the electrical structure of arechargeable battery equipped with a battery protection circuit;

FIG. 24A is a top view, FIG. 24B is a front view, FIG. 24C is a leftside view, FIG. 24D is a right side view, and FIG. 24E is a bottom view,all showing another embodiment of the upper insulation holder;

FIG. 25A is a top view, FIG. 25B is a front view, FIG. 25C is a leftside view, FIG. 25D is a right side view, and FIG. 25E is a bottom view,all showing another embodiment of the lower insulation holder;

FIG. 26 is an oblique view of the rechargeable battery D equipped with abattery protection circuit according to a third embodiment;

FIG. 27 is an oblique view of the assembly structure of rechargeablebattery D in which the various constituent elements thereof areexploded;

FIG. 28A is a plan view of the structure on the top side of the spacer,FIG. 28B is a plan view the underside, and FIG. 28C is a cross sectionalong the XXVIIIC-XXVIIIC line in FIG. 28A;

FIG. 29A is a plan view of the front of the circuit board, and FIG. 29Bis a plan view of the back of the circuit board;

FIG. 30A is a plan view and FIG. 30B is a side view of an intermediateunit;

FIG. 31A is a plan view, FIG. 31B is a side view, FIG. 31C is a planview of the open end, and FIG. 31D is a cross section along theXXXID—XXXID line in FIG. 31B, all showing the bottom of the outer case;

FIG. 32A is an oblique view illustrating the initial state in thesealing of the open end of the outer case, FIG. 32B is an oblique viewillustrating a bent state, and FIG. 32C is an oblique view illustratinga fused state; and

FIG. 33A is a plan view of another embodiment of the sealing pieces,FIG. 33B is a left side view, FIG. 33C is a right side view, and FIG.33D is a plan view Illustrating a bent state.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will now be described throughreference to the appended figures in an effort to facilitate anunderstanding of the present invention. The embodiments given below arespecific examples of the present invention, but are not intended tolimit the technological scope thereof.

The “rechargeable battery equipped with a battery protection circuit”according to the present invention will be hereinafter referred to as“circuit protected cell” to distinguish it from the rechargeable battery10 alone. Various circuit protected cells A to E will be described inthe following various embodiments. Typically, a circuit protected cellin accordance with the present invention comprises a lithium ionrechargeable battery 10 formed in a flat shape (hereinafter referred tomerely as a rechargeable battery), and a battery protection circuitintegrally attached thereto for protecting this rechargeable battery 10from overcharging, overdischarging, and so forth, with the height of therechargeable battery 10 being only slightly increased.

As shown in FIGS. 1A and 1B, the rechargeable battery 10 is in acompact, flat-shaped form in which elements for electromotive force 133are housed in a cell case 26 formed as a bottomed cylinder with an ovalcross section, and the open end of the cell case 26 is sealed by asealing assembly comprising a gasket 135, a sealing plate 132, and anelectrode cap 134. The positive electrode plates that make up part ofthe elements for electromotive force 133 are connected to the electrodecap 134, which is insulated from the cell case 26 by the gasket 135, andthe middle protruding portion of the electrode cap serves as thepositive electrode input and output terminal 25 of the rechargeablebattery 10. The negative electrode plates that make up part of theelements for electromotive force 133 are connected to the cell case 26,and the cell case 26 serves as the negative electrode input and outputterminal of the rechargeable battery 10.

As shown in FIG. 2, the circuit protected cell A according to the firstembodiment is structured such that a positive terminal plate 4, anegative terminal plate 5, and a temperature sensing terminal plate 6are exposed at the top, and the rechargeable battery 10 and the batteryprotection circuit are integrally incorporated into a casing coveredaround its sides with an insulating label 7. FIG. 3 is an exploded viewof the internal structure of this circuit protected cell, which isprovided with the rechargeable battery 10; a connection piece 11 joinedto the positive electrode input and output terminal (protrudingterminal) of this rechargeable battery 10; a central spacer 12 that isdisposed on the top surface of this connection piece 11 and provides aseat for the middle part of a circuit board 9; a peripheral spacer 13that is formed in an oval ring shape, keeps the rechargeable battery 10apart from the circuit board 9, and provides a seat for the circuitboard 9; a circuit board 9 that constitutes the battery protectioncircuit and has formed on it the positive terminal plate 4 and thetemperature sensing terminal plate 6; a cover plate 14 formed by resinmolding and provided with a positive terminal window 18 and atemperature sensing terminal window 19 through which the positiveterminal plate 4 and the temperature sensing terminal plate 6 formed onthis circuit board 9 are exposed to the outside; and a cover cap 15 thatenvelops the various constituent elements disposed on the rechargeablebattery 10, comes into contact with the cell case 26 that serves as thenegative electrode input and output terminal of the rechargeable battery10, and covers the outer peripheral surface of this cell case 26. Theseconstituent elements are assembled on the rechargeable battery 10 asshown in the cross section of FIG. 4.

First, the connection piece 11 is joined to the positive electrode inputand output terminal 25 of the rechargeable battery 10, leads 11 a formedextending from both ends of this connection piece 11 are passed throughopenings 12 a of the central spacer 12, whereby the central spacer 12 isdisposed on the connection piece 11. When the peripheral spacer 13 isplaced around the periphery of the rechargeable battery 10, the tops ofthe central spacer 12 and the peripheral spacer 13 are aligned at thesame height, so the circuit board 9 can be stably placed over these.

FIG. 5A shows the structure on the underside of the circuit board 9, andFIG. 5B the structure on the top side of the circuit board 9. The leads11 a of the connection piece 11 are passed through lead holes 23 formedin the circuit board 9, and are bent over on the top of the circuitboard 9 and soldered in place on the conductor pattern.

As shown in FIG. 5A, an IC 16 which constitutes a battery protectioncircuit that protects the rechargeable battery 10 from overcharging andoverdischarging, a PTC element 17 that prevents excessive current, athermistor 20 that senses the temperature of the rechargeable battery 10and the IC 16, and so forth are disposed on the underside of the circuitboard 9. As shown in FIG. 5B, the positive terminal plate 4 and thetemperature sensing terminal plate 6 are disposed on the top side of thecircuit board 9, joined to the conductor pattern formed on thesubstrate. The conductor pattern formed on the top side of this circuitboard 9 is connected to the conductor pattern formed on the underside bythrough holes 21 at the required places. Since conductor patterns areformed on the top side and the underside at the places where the IC 16is provided, the IC 16 is shielded by the conductor patterns, and thisreduces the incidence of malfunction of the IC 16 caused byelectromagnetic waves, such as wave fogging, even when this circuitprotected cell is used in a cellular telephone or the like.

A cover plate 14, in which a positive terminal window 18 and atemperature sensing terminal window 19 are made at locationscorresponding to the positive terminal plate 4 and the temperaturesensing terminal plate 6, is disposed on the top side of the circuitboard 9. Here, as shown in FIG. 4, on top side, that is, the oppositeside from where the IC 16 is provided on the underside, a gap g of atleast 0.1 mm is provided between the cover plate 14 and circuit board 9.This keeps pressure from being applied to the IC 16 in the event thatexternal pressure should be applied by vibration, impact, or the like,and changes in the electrical performance that would be caused bydeformation of the IC 16 by this pressure can be prevented by providingthe gap g.

A cover cap 15 covers the periphery of this cover plate 14, and thiscover cap 15 also covers the entire peripheral sides of the rechargeablebattery 10. As shown in FIG. 3, connecting pieces 27 formed at fourplaces around the top edge of the cover cap 15 are soldered toconnection patterns 28 formed at four places on the top side of thecircuit board 9, and the ground potential of the circuit board 9 isconnected to the cover cap 15 which is in contact with the cell case 26,which is the negative electrode input and output terminal of therechargeable battery 10. With this connection structure, the top sideend of the cover cap 15 functions as the negative terminal plate 5. Asshown in FIG. 3, cutouts 29 formed at two places along each of the longside surfaces of the cover cap 15 are bent inward until they hit theupper periphery of the rechargeable battery 10, which snugly fits thecover cap 15 to the rechargeable battery 10, and at the same time, theopenings left after the cutouts 29 have been bent function as gas escapeholes for releasing any abnormal pressure in the rechargeable battery10. These gas escape holes open out on the sides, so in the unlikelyevent that gas should spurt from the rechargeable battery 10, it willspurt out from the openings that are perpendicular to the spurtingdirection, which weakens the spurting pressure. The openings produced bythese cutouts 29 are hidden by the insulating label 7 when the sideperipheral surfaces of the cover cap 15 are covered with the insulatinglabel 7, but as shown in FIG. 2, perforated lines 33 are made in theinsulating label 7 at locations corresponding to the cutouts 29, andthese perforated lines 33 tear out in the event of a gas eruption. Also,notches 31 are formed at four places in the peripheral spacer 13 toaccommodate the inward bending of the cutouts 29, and this provides gasescape channels.

A modification can be made, as shown in FIG. 6A, such that theperipheral spacer 13 and the central spacer 12 are integrated into asingle spacer 22. As shown in FIG. 6B, in the middle of the underside ofthis spacer 22 are formed positioning tabs 32 a that fit into thepositive electrode input and output terminal 25 of the cell 10, andpositioning tabs 32 b that fit into a crimp recess around the peripheryof the top side, and this makes it easy to position the spacer 22 on therechargeable battery 10.

As shown in FIG. 2, the circuit protected cell structured as aboveallows the battery protection circuit to be housed internally merely byextending the height of the rechargeable battery 10 a small amount. Whenthis circuit protected cell is installed in a device, reliability ishigher since it has its own battery protection function. Also, thepositive terminal (+), the negative terminal (−), and the temperaturesensing terminal (T) are disposed asymmetrically to the left and righton the top, which prevents the cell from being installed backwards inthe device.

FIG. 7 shows the electrical circuit structure of the circuit protectedcell A described above. The electrical structure of this circuitprotected cell will now be described through comparison of thiselectrical circuit with the structures shown in FIGS. 2 to 5A and 5B.

The cell case 26 that constitutes the negative electrode input andoutput terminal of the rechargeable battery 10 is connected to the covercap 15, and the negative terminal plate 5 is exposed at the top end ofthe circuit protected cell. Meanwhile, the positive electrode input andoutput terminal 25 is connected to the circuit board 9 by the connectionpiece 11, connected to the PTC element 17 disposed on the circuit board9, and connected to the positive terminal plate 4 through an FET 34included in the IC 16. The PTC element 17 generates heat as a result ofexcessive current due to temperature-resistance changes in its positivecharacteristics, and as the temperature rises, resistance increases andprevents excessive current from building up. The FET 34 is turned on andoff by a control circuit 35 that detects overcharging oroverdischarging, and protects the rechargeable battery 10 fromovercharging or overdischarging by cutting off the positive circuit inthe event of overcharging or overdischarging.

The thermistor 20 provided on the underside of the circuit board 9 asshown in FIG. 5A, that is, on the rechargeable battery 10 side, isconnected to the temperature sensing terminal plate 6, reacts totemperature changes in the rechargeable battery 10, and varies theresistance thereof, so when the device in which this circuit protectedcell is used is connected to the temperature sensing terminal plate 6,the temperature of the circuit protected cell can be sensed in order todeal with any abnormal rise in temperature. Also, as shown in FIG. 5A,the thermistor 20 is connected to the conductor pattern 30 at thelocation where the IC 16 is disposed, so temperature changes in the IC16 impart a temperature change to the thermistor 20 by thermalconduction through the conductor pattern 30, which varies theresistance, so temperature changes in the IC 16 can also be detected.Therefore, any abnormal rise in temperature of the IC 16 accompanying arise in temperature of the rechargeable battery 10 on the device sidecan also be detected.

The connection piece 11, the cover cap 15, the positive terminal plate4, and the temperature sensing terminal plate 6 in the circuit protectedcell described above are made from a nickel-copper alloy, so that thereis better compatibility to joining by soldering, spot welding, and soforth. For instance, the connection piece 11 may be joined to thepositive electrode input and output terminal 25 of the rechargeablebattery 10 by spot welding or ultrasonic welding, and the leads 11 aextending from both ends of this connection piece 11 may be soldered tothe conductor pattern of the circuit board 9. Even when a single memberis joined at different portions by different methods, a nickel-copperalloy is compatible with both of the joining methods, allowing a goodjoint to be obtained. Similarly, with the cover cap 15, the connectingpieces 27 may be soldered to the circuit board 9, and the rechargeablebattery 10 may be joined to the cell case 26 by ultrasonic welding orspot welding, and once again a nickel-copper alloy is compatible withboth of these joining methods. Also, the positive terminal plate 4, thetemperature sensing terminal plate 6, and the negative terminal plate 5formed on top end of the cover cap 15 serve as connection contacts thatconduct current through contact with the connection probes of the devicein which this circuit protected cell is used, and lower contactresistance can be achieved by using a nickel-copper alloy.

Modified structures of connection piece are shown denoted at 36 and 37in FIGS. 8A and 8B, wherein the connection piece 11 for connecting thepositive electrode input and output terminal 25 of the rechargeablebattery 10 to the circuit board 9 is combined with the central spacer12. The central spacer 12 supporting the middle part of the circuitboard 9 is eliminated and its support function is given to theconnection piece 36 or 37. The connection pieces 36 and 37 have bases 36b and 37 b, respectively, that are formed in a thickness correspondingto the gap between the positive electrode input and output terminal 25and the circuit board 9, and from the ends of which extend leads 36 aand 37 a, respectively. When the connection piece 36 or the connectionpiece 37 is joined on the positive electrode input and output terminal25 and the circuit board 9 disposed thereon, the middle part of thecircuit board 9 is supported in a stable state, so it can adequatelywithstand the contact pressure of the connection probe on the deviceside that connected by contact with the positive terminal plate 4disposed in the middle part of the circuit board 9.

With the structure of the present invention as described above, theconnection pieces 11, 36, and 37 can consist of a PTC element, whichallows the PTC element 17 provided on the circuit board 9 to beeliminated and thereby increases the available space on the circuitboard 9, which is preferable for applications to smaller rechargeablebatteries 10.

The rechargeable battery 10 in this embodiment is a lithium ionrechargeable battery in which the positive electrode input and outputterminal 25 is used for the sealing assembly and the cell case 26 forthe negative electrode input and output terminal, but it should gowithout saying that a rechargeable battery in which the negativeelectrode is on the sealing assembly side and the positive electrode onthe cell case side is also acceptable, and that modifications may bemade in the connections.

Next, a rechargeable battery equipped with a battery protection circuit(circuit protected cell B) according to the second embodiment will bedescribed. The circuit protected cell B in the following embodimentcomprises a flat-shaped lithium ion rechargeable battery as shown inFIGS. 1A and 1B, and a circuit board 109 which constitutes a protectioncircuit that protects against overcharging, overdischarging, and soforth, which is integrally attached to the battery as shown in FIGS. 9A,9B, and 9C.

In FIGS. 9A to 9C, the circuit protected cell B according to thisembodiment has a positive terminal plate 104, a negative terminal plate105, and a temperature sensing terminal plate 106 exposed on the outsideof one end thereof, and everything other than this terminal portion iscovered by an upper insulation board 113, a lower insulation board 114,and an insulating label 107. Inside, the rechargeable battery 10 and acircuit board 109 that constitutes a battery protection circuit areintegrally incorporated.

FIG. 10 is an exploded view of the internal structure of the circuitprotected cell B. On the sealing assembly side of the rechargeablebattery 10 (structured as a lithium ion rechargeable battery) aredisposed a connection piece 111 joined to the positive electrode inputand output terminal (protruding terminal) 25 of this rechargeablebattery 10; a spacer 112 that is disposed on the rechargeable battery 10and provides a seat for the circuit board 109; a circuit board 109 thatconstitutes the battery protection circuit and has formed on it thepositive terminal plate 104, the negative terminal plate 105, and thetemperature sensing terminal plate 106; and the upper insulation board113 that insulates and covers this circuit board 109 from above. On thebottom side of the rechargeable battery 10 there are disposed a leadplate 110 that is joined to the bottom surface of the rechargeablebattery 10 and has a pair of leads 110 a extending to the sealingassembly side, and the lower insulation board 114 that insulates andcovers the bottom of the rechargeable battery 10.

As shown in FIG. 11, the connection piece 111, which is formed with abox section, consists of a base 111 b and leads 111 a. The base 111 b isjoined to the positive electrode input and output terminal 25 of therechargeable battery 10. As shown in FIG. 12, the lead plate 110, whichis also formed with a box section, consists of a base 110 b and a pairof leads 110 a. The base 110 b is joined to the bottom surface of thecell case 26 of the rechargeable battery 10 as shown in FIG. 10. Thepair of leads 110 a extend along the sides of the cell case 26 towardthe sealing assembly.

The spacer 112, which is formed as shown in FIGS. 13A to 13C, isattached on the sealing assembly side of the rechargeable battery 10. Asshown in FIG. 13C, a positioning lug 137 that mates with the positiveelectrode input and output terminal 25 of the rechargeable battery 10,and insertion lugs 140 that are inserted into recesses on the sealingassembly side of the rechargeable battery 10 are formed on the undersideof the spacer 112, and these lugs are used to fit and position thespacer 112 on the rechargeable battery 10. This spacer 112 is coatedwith a UV adhesive agent, fitted on the sealing assembly side of therechargeable battery 10, and fixed on the rechargeable battery 10 bycuring the UV adhesive by ultraviolet irradiation. A connection piecehole 138 is made in the spacer 112, and the leads 111 a of theconnection piece 111 joined to the positive electrode input and outputterminal 25 are passed through this connection piece hole 138. Thisspacer 112 forms a flat seat away from the rechargeable battery 10, andrecesses 136 for accommodating the electronic parts mounted on thecircuit board 109 are formed in this seat. Therefore, when the circuitboard 109 is placed on the seat of the spacer 112, the electronic partsfit into the recesses 136, and the circuit board 109 is stacked up onthe rechargeable battery 10 only in the thickness of its substrate,which minimizes the increase in volume caused by providing the batteryprotection circuit.

FIG. 14A shows the structure on the front of the circuit board 109,while FIG. 14B shows the structure on the back of the circuit board 109.The battery protection circuit shown in FIG. 15 is formed on the circuitboard 109. As shown in FIG. 14B, the battery protection circuit isformed on the back of the circuit board 109, and as shown in FIG. 14A,on the front are formed the positive terminal plate 104, the negativeterminal plate 105, the temperature sensing terminal plate 106,connection piece conductor patterns 115 a and 115 b for connecting theconnection piece 111, and lead plate conductor patterns 116 a and 116 bfor connecting the lead plate 110. The circuit patterns formed on thetwo sides are connected by through holes 130 where required. The pair ofleads 111 a of the connection piece 111 are passed through lead holes120 formed in this circuit board 109, and the leads 111 a are bent overand soldered on the connection piece conductor patterns 115 a and 115 b,respectively. The pair of leads 110 a of the lead plate 110 are passedinto lead plate notches 129 formed at both ends of the circuit board109, and are bent over and soldered on lead plate conductor patterns 116a and 116 b. This soldering of the respective pairs of leads 111 a and110 a of the connection piece 111 and lead plate 110 fixes the circuitboard 109 on the spacer 112.

The battery protection circuit shown in FIG. 15 is equipped with a maincontrol circuit IC 121 for protecting the rechargeable battery 10against overcharging, overdischarging, and excessive current. Whenvoltage indicating a state of overcharging, overdischarging, orexcessive current is detected, an FET (a switching element) incorporatedin the IC is turned off and kept off by hysteresis until a specificrelease voltage is detected, and the input and output terminals of therechargeable battery 10 are cut off to protect the rechargeable battery10 from overcharging, overdischarging, and excessive current. While theinput and output terminals are cut off due to overcharging, it ispossible for power to flow in the discharge direction, and while theinput and output circuits are cut off due to overdischarging, it ispossible for power to flow in the charge direction. A sub-controlcircuit IC 122 for protecting the rechargeable battery 10 fromovercharging is provided in addition to the main control circuit IC 121.During normal operation, the sub-control circuit IC 122 keeps the inputand output circuits on by turning on a power MOSFET 123 connected inseries with the input and output circuits. If the operation to preventovercharging is not performed due to a malfunction in the main controlcircuit IC 121, the sub-control circuit IC 122 senses how far theovercharging has progressed, turns off the power MOSFET 123 to cut offthe input and output circuits, keeps it off by hysteresis until aspecific release voltage is detected, and prevents damage to therechargeable battery 10 by overcharging. With this structure, therechargeable battery 10 is protected redundantly from overcharging,which allows the rechargeable battery 10 which would be damagedparticularly badly by overcharging to be protected by the batteryprotection circuit. Therefore, it is possible to eliminate the PTCelement or current cut-off vent that used to be provided in a cell inorder to protect the cell, and this structure is a favorable means forprotection in the case of a small, thin rechargeable battery 10 as inthis embodiment. More specifically, with a small, thin cell, it isdifficult to find enough space to provide a PTC element or currentcut-off vent, and if one is provided it reduces the volume of thepositive and negative electrodes that serve as the elements forelectromotive force, and the cell capacity has to be reduced and cellperformance compromised, but this problem is eliminated with thestructure in this embodiment. Also, if a PTC element is used as part ofthe battery protection circuit, it will take up more of the space in thebattery protection circuit and make it difficult to produce a smallcell, but the battery protection circuit of the present structure doesnot need to make use of a PTC element.

As shown in FIG. 14A, the positive terminal plate 104 is joined on apositive terminal conductor pattern 104 a formed on the front of thecircuit board 109, the negative terminal plate 105 is joined on anegative terminal conductor pattern 105 a, and the temperature sensingterminal plate 106 is joined on a temperature sensing terminal conductorpattern 106 a. These terminals have superior electroconductivity,joinability, and corrosion resistance because they are made from a sheetof copper-nickel alloy, a clad material comprising a sheet ofcopper-nickel alloy and stainless steel, or the like. The terminals neednot be joined as sheets, and the various conductor patterns can insteadthemselves be utilized directly as terminals.

As described above, the result of mounting the spacer 112 and thecircuit board 109 on the rechargeable battery 10 is that therechargeable battery 10 is connected to the battery protection circuitformed on the circuit board 109, as shown in the circuit diagram in FIG.15. The input and output of the rechargeable battery 10 go through thisbattery protection circuit, resulting in a circuit protected cell E asshown in FIG. 16. This circuit protected cell E can be housed in a lowercase 141 having formed in it a positive terminal window 104 b, anegative terminal window 105 b, and a temperature sensing terminalwindow 106 b as shown in FIG. 16, and when the lower case 141 is closedwith an upper case 142, the resulting configuration is a battery pack.

The circuit protected cell E is subjected to the processing describedbelow in order to obtain the configuration of the circuit protected cellillustrated in FIGS. 9A to 9C. Just as shown in FIG. 10, the upperinsulation board 113 is disposed on top of the circuit board 109, thelower insulation board 114 is disposed on the bottom of the rechargeablebattery 10, and the insulating label 107 covers the entire sideperipheral surface, including the area around the upper insulation board113 and the lower insulation board 114, resulting in the sameconfiguration as the circuit protected cell illustrated in FIGS. 9A to9C.

As shown in FIGS. 17A, 17B, and 17C, the upper insulation board 113 hasformed in it a positive terminal window 104 c at a locationcorresponding to the positive terminal plate 104 provided to the circuitboard 109, a negative terminal window 105 c at a location correspondingto the negative terminal plate 105, and a temperature sensing terminalwindow 106 c at a location corresponding to the temperature sensingterminal plate 106, around which is formed a step 143 covering the edgeof the insulating label 107. As shown in FIGS. 18A, 18B, and 18C, a leadgroove 144 for accommodating the lead plate 110 is formed on the innersurface side of the lower insulation board 114, and a curved surfacematching the shape of the bottom surface of the rechargeable battery 10is formed around this. As shown in FIG. 18C, a step 145 covering theedge of the insulating label 107 is formed around the outer periphery.

The insulating label 107 is formed by applying an adhesive to aheat-shrinkable sheet. At the same time it is stuck onto the variousconstituent members, it is heat-shrunk so as to cover these members,thereby integrating the parts. A design can be printed on the surface ofthis insulating label 107, which allows the outer shell to have anattractive appearance and also allows usage instructions, warnings, orthe like to be indicated.

As shown in FIGS. 9A to 9C, with a rechargeable battery equipped with abattery protection circuit structured as above, the battery protectioncircuit can be housed internally merely by extending the height of therechargeable battery 10 a small amount, and when this cell is installedin a device, reliability is higher since the rechargeable battery itselfhas a battery protection function. Also, the positive terminal 104, thenegative terminal 105, and the temperature sensing terminal 106 aredisposed asymmetrically to the left and right on the top, which preventsthe cell from being installed backwards in the device.

The main application for the flat-shaped rechargeable battery 10 is as apower source for small, portable electronic devices, and increasing thethickness sacrifices the advantages of the flat shape, but with thepresent structure, a battery protection circuit can be provided withoutincreasing the thickness of the rechargeable battery 10, with the finalconfiguration being not a battery pack, but a smaller, more lightweightrechargeable battery equipped with a battery protection circuit, whichhelps make compact, portable electronic devices smaller and morelightweight.

A thermistor 124 is connected to the temperature sensing terminal 106,and this thermistor 124 is disposed at a location close to the maincontrol circuit IC 121 of the circuit board 109 toward the rechargeablebattery 10. The thermistor 124 varies its resistance by reacting to thetemperature of the rechargeable battery 10 and the main control circuitIC 121, so when it is connected to the temperature sensing terminalplate 106 with the device in which this rechargeable battery equippedwith a battery protection circuit is used, the temperature is monitoredto deal with any abnormal increases in temperature.

Next, the rechargeable battery equipped with a battery protectioncircuit (circuit protected cell C) according to the third embodimentwill be described.

In FIG. 19, the circuit protected cell C according to this embodimenthas a positive terminal 204, a negative terminal 205, and a temperaturesensing terminal 206 exposed to the outside at one end, and other thanthese terminal portions, everything is covered by an upper insulatingholder 213, a lower insulating holder 214, and an insulating sheet 207,inside of which the rechargeable battery 10 and the circuit board 209 onwhich the battery protection circuit is formed are integrallyincorporated.

FIG. 20 is an exploded view of the internal structure of the circuitprotected cell C. On the sealing assembly side of the rechargeablebattery 10 (structured as a lithium ion rechargeable battery) aredisposed a connection piece 211 joined to the positive electrode inputand output terminal (protruding terminal) 25 of the rechargeable battery10; a spacer 212 that is disposed on the rechargeable battery 10 andprovides a seat for the circuit board 209; a circuit board 209 thatconstitutes the battery protection circuit and has formed on it thepositive terminal 204, the negative terminal 205, and the temperaturesensing terminal 206; and the upper insulation board 213 that insulatesand covers the top side. On the bottom side of the rechargeable battery10 are disposed a pair of lead plates 210 whose bases 210 b are joinedto the bottom surface of the rechargeable battery 10 and whose leads 210a extend to the sealing assembly side, and the lower insulation board214 that insulates and covers the bottom side.

The base 211 b of the L-shaped connection piece 211 is joined to thepositive electrode input and output terminal 25 of the rechargeablebattery 10. The bases 210 b of the pair of lead plates 210 are joined tothe bottom surface of the cell case 26, and the pair of leads 210 aextend along the sides of the cell case 26 toward the sealing assembly.

The spacer 212, which is formed as shown in FIGS. 21A to 21C, isattached on the sealing assembly side of the rechargeable battery 10. Asshown in FIG. 21B, a pair of positioning lugs 237 that hit the long sidesurfaces of the rectangularly formed positive electrode input and outputterminal 25 are formed on the underside (the rechargeable battery 10side) of the spacer 212, and these are disposed on the sealing assemblyso as to mate with the positive electrode input and output terminal 25,the result of which is that the spacer 212 is positioned to fit over therechargeable battery 10, and insulation from the cell case 26 serving asthe negative electrode is improved.

A connection piece hole 238 between the pair of positioning lugs 237allows the lead 211 a of the connection piece 211 joined to the positiveelectrode input and output terminal 25 to be passed through to the topsurface. The spacer 212 forms a seat insulated from the rechargeablebattery 10, and in this seat are formed openings 236 a and 236 b thataccommodate the electronic parts mounted on the sealing assembly side ofthe circuit board 209. When the circuit board 209 is placed on thisseat, the electronic parts mounted on the sealing assembly side fit intothe openings 236 a and 236 b, so the circuit board 209 is stacked up onthe rechargeable battery 10 only in a height equal to the thickness ofits substrate and the thickness of the spacer 212, which minimizes theincrease in height caused by providing the battery protection circuit.

FIGS. 22A and 22B show in see-through fashion the conductor patternsformed on the front and back of the circuit board 209 and the electronicparts mounted thereon, in which the battery protection circuit and inputand output circuits shown in FIG. 23 are formed on a substrate. As shownin FIG. 22B, a battery protection circuit in which IC parts 221 and 222and chip parts 226 are mounted is formed on the back of the circuitboard 209. As shown in FIG. 22A, on the front are formed the positiveterminal 204, the negative terminal 205, the temperature sensingterminal 206, a connection piece conductor pattern 215 for connectingthe connection piece 211, and lead plate conductor patterns 216 a and216 b for connecting the lead plates 210. The circuit patterns formed onthe two sides are connected by through holes 230 where required.

The leads 211 a of the connection piece 211 are passed through leadholes 220 formed in this circuit board 209, and the leads 211 a are bentover and soldered on the connection piece conductor pattern 215. Theleads 210 a of the pair of lead plates 210 are passed into lead platenotches 229 formed at both ends of the circuit board 209, and are bentover and soldered on the lead plate conductor patterns 216 a and 216 b.This soldering of the connection piece 211 and lead plates 210 fixes thecircuit board 209 on the spacer 212.

The battery protection circuit shown in FIG. 23 is equipped with themain control circuit 221 for protecting the rechargeable battery 10against overcharging, overdischarging, and excessive current. Whenvoltage indicating a state of overcharging, overdischarging, orexcessive current is detected, a switching device incorporated in the ICis turned off and.kept off by hysteresis until a specific releasevoltage is detected, and the input and output circuits of therechargeable battery 10 are cut off to protect the rechargeable battery10 from overcharging, overdischarging, and excessive current. While theinput and output circuits are cut off due to overcharging, it ispossible for power to flow in the discharge direction, and while theinput and output circuits are cut off due to overdischarging, it ispossible for power to flow in the charge direction. A sub-controlcircuit IC 222 for protecting the rechargeable battery 10 fromovercharging is provided in addition to the main control circuit IC 221.During normal operation, the sub-control circuit IC 222 keeps the inputand output circuits on by turning on a switching device incorporatedinto the IC. If the operation to prevent overcharging is not performeddue to a malfunction in the main control circuit IC 221, the sub-controlcircuit IC 222 senses how far the overcharging has progressed, turns offthe switching device to cut off the input and output circuits, keeps itoff by hysteresis until a specific release voltage is detected, andprevents damage to the rechargeable battery 10 by overcharging. Withthis structure, the rechargeable battery 10 is protected redundantlyfrom overcharging, which allows the rechargeable battery 10 which wouldbe damaged particularly badly by overcharging to be protected by thebattery protection circuit. Therefore, it is possible to eliminate thePTC element or current cut-off vent that used to be provided in a cellin order to protect the cell, and this structure is a favorable meansfor protection in the case of a small, thin rechargeable battery 10 asin this embodiment. More specifically, with a small, thin cell, it isdifficult to find enough space to provide a PTC element or currentcut-off vent, and if one is provided it reduces the volume of thepositive and negative electrodes that serve as the elements forelectromotive force, and the cell capacity has to be reduced and cellperformance compromised, but this problem is eliminated with thestructure in this embodiment. Also, if a PTC element is used as part ofthe battery protection circuit, it will take up more of the space in thebattery protection circuit and make it difficult to produce a smallcell, but the battery protection circuit of the present structure doesnot need to make use of a PTC element.

With the circuit board 209 on which this battery protection circuit isformed, as shown in FIG. 22B, a main ground pattern 219 connected viathrough holes 230 from the lead plate conductor pattern 216 b to whichone of the pair of lead plates 210 is connected is not directlyconnected to a sub-ground pattern 218 connected via the through holes230 from the lead plate conductor pattern 216 a to which the other leadplate 210 is connected. This circuit structure avoids the formation of aclosed circuit in which the pair of lead plates 210 whose bases 210 bare joined to the cell case 26 are linked by the conductor pattern onthe circuit board 209. If a closed circuit is formed, the cell will bemore susceptible to noise and the like from the device in which it isused, but malfunction due to noise or the like can be prevented byemploying the above structure in which no closed circuit is formed.

As shown in FIG. 22A, the positive terminal 204 is joined on a positiveterminal conductor pattern 204 a formed on the front of the circuitboard 209, the negative terminal 205 is joined on a negative terminalconductor pattern 205 a, and the temperature sensing terminal 206 isjoined on a temperature sensing terminal conductor pattern 206 a. Theseterminals have superior electroconductivity, joinability, and corrosionresistance because they are made from a sheet of copper-nickel alloy, aclad material comprising a sheet of copper-nickel alloy and stainlesssteel, or the like. The terminals need not be joined as sheets, and thevarious conductor patterns can instead be metal plated and utilizeddirectly as terminals.

After the circuit board 209 has been attached as above to therechargeable battery 10, as shown in FIG. 20 the upper insulating holder213 is disposed on top of the circuit board 209, the lower insulatingholder 214 is disposed on the bottom of the rechargeable battery 10, andthe insulating label 207 covers the entire side peripheral surface,including the area around the upper insulation holder 213 and the lowerinsulation holder 214, thereby completing the circuit protected cell Cconfigured as shown in FIG. 19.

As shown in FIG. 20, the upper insulating holder 213 has formed in it apositive terminal window 204 c at a location corresponding to thepositive terminal 204 provided to the circuit board 209, a negativeterminal window 205 c at a location corresponding to the negativeterminal 205, and a temperature sensing terminal window 206 c at alocation corresponding to the temperature sensing terminal 206, aroundwhich is formed a step 243 covering the edge of the insulating label207. As shown in FIG. 20, lead grooves 241 for accommodating the leadplate 210 are formed on the inner surface sides of the upper insulatingholder 213 and the lower insulating holder 214.

The upper insulating holder 213 and the lower insulating holder 214 canrespectively be modified as shown in FIGS. 24A to 24E and FIGS. 25A to25E. That is, they can be open at locations corresponding to the leadplates 210, and be divided into extensions 213 a and 214 a,respectively, which affords a reduction in the width of the upperinsulating holder 213 and lower insulating holder 214, and allows theoverall size to be smaller. Also, if linking notches 213 b and 214 bthat fit together are provided at the abutting distal ends of theextensions 213 a and 214 a, respectively, then the upper insulatingholder 213 and the lower insulating holder 214 will be securely linkedtogether. Furthermore, the upper insulating holder 213 and the lowerinsulating holder 214 can be securely linked together by providing tabs248 and openings 249 that fit together to the linking notches 213 b and214 b, respectively, so that the upper insulating holder 213 and thelower insulating holder 214 can be engaged.

If, as shown in FIG. 20, covering components 244 that cover the upperand lower parts of the long side surfaces of the rechargeable battery 10are formed on the upper insulating holder 213 and the lower insulatingholder 214, it will be easier to fit these holders onto the rechargeablebattery 10 and easier to wrap the insulating sheet 207 around it. Thesecovering components 244 can also be provided in the structures shown inFIGS. 24A to 24E and FIGS. 25A to 25E, and since the side surfaces ofthe rechargeable battery 10 are not entirely covered, there will be roomfor the cell case 26 to expand, which minimizes changes in the overallthickness in the event that swelling should occur. The rechargeablebattery 10 generates gas through high-temperature discharge in a fullycharged state or repeated charging and discharging, and the mechanicallyweak middle section of the cell case 26 has a tendency to swell, butsince this swelling is absorbed within the thickness of the coveringcomponents 244, the adverse effects caused by changes in the thicknessof the rechargeable battery 10 are avoided.

After the upper insulating holder 213 and the lower insulating holder214 have been attached to the rechargeable battery 10 as above, theinsulating sheet 207 is stuck to the peripheral side surface from thestep 243 of the upper insulating holder 213 and below. The insulatingsheet 207 is formed by applying an adhesive to a heat-shrinkable sheet.At the same time it is stuck onto the various constituent members, it isheat-shrunk so as to cover these members, thereby integrating the parts.A design can be printed on the surface of this insulating label 207,which allows the outer shell to have an attractive appearance and alsoallows usage instructions, warnings, or the like to be indicated.

As shown in FIG. 19, with a rechargeable battery equipped with a batteryprotection circuit structured as above, the battery protection circuitcan be housed internally merely by extending the height of therechargeable battery 10 a small amount, and when this cell is installedin a device, reliability is higher since the rechargeable battery itselfhas a battery protection function. Also, the positive terminal 204, thenegative terminal 205, and the temperature sensing terminal 206 aredisposed asymmetrically to the left and right on the top, which preventsthe cell from being installed backwards in the device.

The rechargeable battery 10 in this embodiment has been described, asone example, as a lithium ion rechargeable battery in which the positiveelectrode input and output terminal 25 is used for the sealing assemblyand the cell case 26 for the negative electrode input and outputterminal, but it should go without saying that a rechargeable battery inwhich the negative electrode is on the sealing assembly side and thepositive electrode on the cell case side is also acceptable, and thatmodifications may be made in the connections.

Next, a rechargeable battery equipped with a battery protection circuit(circuit protected cell D) according to a fourth embodiment will bedescribed.

In FIG. 26, the circuit protected cell D according to this embodiment issuch that the rechargeable battery 10 and a circuit board 309 on which abattery protection circuit is formed are housed in an outer case 307formed by resin molding, and a positive terminal 304, a negativeterminal 305, and a temperature sensing terminal 306 are exposed to theoutside at one end.

FIG. 27 is an exploded view of the internal structure of the circuitprotected cell D. On the sealing assembly side of the rechargeablebattery 10 (structured as a lithium ion rechargeable battery) aredisposed a connection piece 311 joined to the positive electrode inputand output terminal (protruding terminal) 25 of this rechargeablebattery 10; a spacer 312 that is disposed on the rechargeable battery 10and provides a seat for the circuit board 309; and a circuit board 309that constitutes the battery protection circuit and has formed on it thepositive terminal 304, the negative terminal 305, and the temperaturesensing terminal 306. On the bottom side of the rechargeable battery 10there is disposed a lead plate 310 whose base 310 b is joined to thebottom surface of the rechargeable battery 10 and whose lead 310 aextends to the sealing assembly side.

The base 311 b of the L-shaped connection piece 311 is joined to thebottom surface of the rechargeable battery 10. The base 310 b of thelead plate 310 is joined to the bottom surface of the cell case 26, andthe lead 310 a extends along the side of the cell case 26 toward thesealing assembly.

The spacer 312, which is formed as shown in FIGS. 28A to 28C, isattached on the sealing assembly side of the rechargeable battery 10. Asshown in FIG. 28B, a pair of positioning lugs 337 that hit the long sidesurfaces of the rectangularly formed positive electrode input and outputterminal 25 are formed on the underside (the rechargeable battery 10side) of the spacer 312, and these are disposed on the sealing assemblyso as to mate with the positive electrode input and output terminal 25,the result of which is that the spacer 312 is positioned to fit over therechargeable battery 10.

A connection piece hole 338 between the pair of positioning lugs 337allows the lead 311 a of the connection piece 311 joined to the positiveelectrode input and output terminal 25 to be passed through to the topsurface. The spacer 312 forms a seat insulated from the rechargeablebattery 10, and in this seat are formed openings 336 a and 336 b thataccommodate the electronic parts mounted on the sealing assembly side ofthe circuit board 309. When the circuit board 309 is placed on thisseat, the electronic parts mounted on the sealing assembly side fit intothe openings 336 a and 336 b, so the circuit board 309 is stacked up onthe rechargeable battery 10 only in a height equal to the thickness ofits substrate and the thickness of the spacer 312, which minimizes theincrease in height caused by providing the battery protection circuit.

FIGS. 29A and 29B show in see-through fashion the conductor patternsformed on the front and back of the circuit board 309 and the electronicparts mounted thereon, in which the battery protection circuit and inputand output circuits shown in FIG. 23 are formed on a substrate. As shownin FIG. 29B, a battery protection circuit in which IC parts 221 and 222and chip parts 326 are mounted is formed on the back of the circuitboard 309. As shown in FIG. 29A, on the front are formed the positiveterminal 304, the negative terminal 305, the temperature sensingterminal 306, a connection piece conductor pattern 315 for connectingthe connection piece 311, and a lead plate conductor pattern 316 forconnecting the lead plate 310. The circuit patterns formed on the twosides are connected by through holes 330 where required. The lead 311 aof the connection piece 311 is passed through a lead hole 320 formed inthis circuit board 309, and the lead 311 a is bent over and soldered onthe connection piece conductor pattern 315. The lead 310 a of the leadplate 310 is passed into a lead plate notch 329 formed at the end of thecircuit board 309, and is bent over and soldered on the lead plateconductor pattern 316. This soldering of the connection piece 311 andthe lead plate 310 fixes the circuit board 309 on the spacer 312.

As shown in FIG. 29A, the positive terminal 304 is joined on a positiveterminal conductor pattern 304 a formed on the front of the circuitboard 309, the negative terminal 305 is joined on a negative terminalconductor pattern 305 a, and the temperature sensing terminal 306 isjoined on a temperature sensing terminal conductor pattern 306 a. Theseterminals have superior electroconductivity, joinability, and corrosionresistance because they are made from a sheet of copper-nickel alloy, aclad material comprising a sheet of copper-nickel alloy and stainlesssteel, or the like. The terminals need not be joined as sheets, and thevarious conductor patterns can instead be metal plated and utilizeddirectly as terminals.

Attaching the circuit board 309 to the rechargeable battery 10 as aboveforms an intermediate unit 350 in which the rechargeable battery 10 andthe circuit board 309 are integrated, as shown in FIG. 30B. Thisintermediate unit 350 is sealed in an outer case 307 formed as shown inFIGS. 31A to 31D, thereby completing the circuit protected cell Dconfigured as shown in FIG. 26.

In FIGS. 31A to 31D, a positive terminal window 304 c provided at alocation corresponding to the positive terminal 304 provided to thecircuit board 309, a negative terminal window 305 c provided at alocation corresponding to the negative terminal 305, and a temperaturesensing terminal window 306 c provided at a location corresponding tothe temperature sensing terminal 306 are made in the bottom of the outercase 307 formed in the shape of a bottomed box. Sealing pieces 313 areformed at the open end for closing the open end after the intermediateunit 350 has been put inside. As shown in FIG. 31D, the cross sectionalshape of the outer case 307 is such that the inner surface thereof isformed in a substantially oval shape corresponding to the shape of theoval rechargeable battery 10, and the outer shape is rectangular withrounded corners. The shape is modified so that the rechargeable battery10 with its oval cross section can be fit snugly inside the device.

The sealing pieces 313 are bent inward by hot pressing, as shown in FIG.32B, after the intermediate unit 350 has been inserted through the openend of the outer case 307 from the circuit board 309 side thereof in thestate shown in FIG. 32A. Then, as shown in FIG. 32C, the opposingsealing pieces 313 are fused/molded by heating and melting, which sealsthe intermediate unit 350 inside the outer case 307. The ends of thesealing pieces 313 are formed thicker as shown in the figures, whichfills in the gap between the opposing sealing pieces 313 when the resinis melted, and ensures that there is enough resin to provide adequatefusion strength.

The sealing pieces 313 can be formed as shown in FIGS. 33A to 33D in acomb shape such that the opposing pieces fit together. The opposingsealing pieces 313 are designed so that there will be a gap between themwhen they are bent over, and this gap is filled in by melting. To ensurethat this gap is filled in and the pieces are securely fused, one orboth rows of the comb teeth 314 of the sealing pieces 313 can be formedthicker than the other portions, which provides enough resin to bemelted.

This intermediate unit 350 that is housed in the outer case 307 may havevariance in its height due to dimensional error in the constituentelements thereof, assembly error, or the like, and this unit may beloose within the outer case 307 if it is smaller than the specifieddimensions, but the molten resin can be allowed to penetrate into theinterior through the gap between the outer case 307 and the intermediateunit 350, which fills in the gaps that cause looseness and absorbs thisdimensional variance. Also, as shown in FIGS. 32A to 32C and FIGS. 33Ato 33D, if protrusions 318 are formed on the inside of the sealingpieces 313, any gaps will be filled in if the intermediate unit 350should be smaller than its specified dimensions, and the height will bereduced if it is larger than its specified dimensions, so variance inthe dimensions of the intermediate unit 350 can be absorbed even moreeffectively.

The open end of the outer case 307 can also be sealed by formingextensions on the four sides around the periphery, and melting these byhot pressing so as to bring the outer case 307 to the specified heightand close the open end. With this sealing means, even if there should bevariance in the height of the intermediate unit 350 as mentioned above,it can be absorbed in the sealing process. Specifically, if theintermediate unit 350 is taller than the specified height, pressureduring hot pressing will be higher, so extra molten resin will flow intothe gap between the outer case 307 and the intermediate unit 350, andthe open end will be sealed with a thin resin layer. On the other hand,if the intermediate unit 350 is shorter than the specified height, thepressure during hot pressing will be lower, so the amount of moltenresin that flows into the gap will be smaller, and the open end will besealed with a thick resin layer.

As shown in FIG. 26, the circuit protected cell D structured as aboveallows the battery protection circuit to be housed internally merely byextending the height of the rechargeable battery 10 a small amount. Whenthis circuit protected cell is installed in a device, the reliability ofthe power source is higher since the cell itself has a batteryprotection function. Also, the positive terminal 304, the negativeterminal 305, and the temperature sensing terminal 306 are disposedasymmetrically to the left and right on the top, which prevents the cellfrom being installed backwards in the device.

The main application for the flat-shaped rechargeable battery 10 is as apower source for small, portable electronic devices, and increasing thethickness sacrifices the advantages of the flat shape, but with thepresent structure, a battery protection circuit can be provided withoutincreasing the thickness of the rechargeable battery 10, with the finalconfiguration being not a battery pack, but a smaller, more lightweightrechargeable battery equipped with a battery protection circuit, whichhelps make compact, portable electronic devices smaller and morelightweight.

The rechargeable battery 10 in this embodiment was a lithium ionrechargeable battery in which the positive electrode input and outputterminal 25 is used for the sealing assembly and the cell case 26 forthe negative electrode input and output terminal, but it should gowithout saying that a rechargeable battery in which the negativeelectrode is on the sealing assembly side and the positive electrode onthe cell case side is also acceptable, and that modifications may bemade in the connections.

INDUSTRIAL APPLICABILITY

As described above, with the present invention, a battery protectioncircuit is an integral part of a rechargeable battery so no battery packstructure need be provided, making it seem as though just the battery isbeing installed in the device. This contributes to reducing the size andweight of devices that use a rechargeable battery as their power source.Also, by increasing the performance of the battery protection circuit, arechargeable battery can be protected from overcharging,overdischarging, excessive current, and so forth without providing a PTCelement or a current cut-off vent, so the function of highly reliablebattery protection can be achieved in a more compact size withoutdecreasing the capacity of the rechargeable battery.

What is claimed is:
 1. A rechargeable battery pack comprising: arechargeable battery having a first electrode and a second electrode; acircuit board disposed at one end on a side of a sealing portion of therechargeable battery; a battery protection circuit for protecting therechargeable battery from overcharging, the battery protection circuitbeing arranged on a side of the circuit board which faces the sealingpotion of the rechargeable battery; a plurality of input and outputterminals being arranged on another side of the circuit board; and aspacer for supporting the circuit board and keeping the circuit boardand the rechargeable battery apart, the spacer including a recess foraccommodating electronic parts mounted on the circuit board, wherein thefirst electrode and the second electrode of the rechargeable battery arerespectively electrically connected to the plurality of input and outputterminals of the circuit board through the battery protection circuit.2. The rechargeable battery pack according to claim 1, furthercomprising a cover cap for covering a peripheral part of therechargeable battery, the cover cap being connected at a specificlocation of the circuit board.
 3. The rechargeable battery according toclaim 1, further comprising a pack case for accommodating therechargeable battery, the spacer, and the circuit board, the pack casehaving a plurality of openings at a location corresponding to each ofthe input and output terminals.
 4. A rechargeable battery equipped witha battery protection circuit according to claim 1, wherein the pluralityof input and output terminals provided on the circuit board are disposedasymmetrically.
 5. A rechargeable battery equipped with a batteryprotection circuit according to claim 1, wherein an IC is provided on alower side of the circuit board, and a conductor pattern connected to aground potential is formed on an upper side of the circuit board atleast at a location, on the backside of which said IC is disposed.
 6. Arechargeable battery equipped with a battery protection circuitaccording to claim 1, wherein a side peripheral surface of therechargeable battery is covered with an electrically insulating sheet.